I recently bought this house (built in 2000), so it went through inspection. I assumed everything was fine. I realized the smoke detector in one of the rooms was not showing the green light that the others were showing. I pressed the "test" button and it beeped just like the others, so I thought it may be okay.
More recently I decided to actually take a look at it, and figured out the black wire is completely disconnected. Googling what that wire means gave me different results, but most of the results suggeste the detector would not be connected to the power, which would mean its battery would end very quickly, but I don't see the detector complaining about the battery (it's been a few months since we moved in).
Now I'm completely confused and have no idea if this is actually safe (especially since the home inspector was supposed to have checked this).
Am I safe? Would it be easy to fix this in case there's a problem? The other detectors in the house are not connected like this one.